Explosives in WWI and WWII Shipwrecks Are Still Polluting the North Sea, Study Finds

Explosives leaking from century-old shipwrecks are polluting parts of the North Sea, according to a study led by Katrine Juul Andresen, a professor at Aarhus University's Department of Geoscience, published in the journal Marine Pollution Bulletin. The research focused on the German submarine UC-30, which sank off the coast of Rømø, Denmark, on April 19, 1917, after striking a British mine while carrying 18 mines and six torpedoes; 27 crew members died, and the wreck was not found until 2016.

Working with Danish Navy divers, since civilian diving on the wreck is not permitted, Andresen's team collected sediment, water and wildlife samples, including starfish and mussels living on the wreck, along with video and photographs used to assess the mines' condition. "We found traces of TNT in the wildlife, the seabed and the water column. Pollution is definitely occurring," Andresen said, adding that the contamination appears relatively localized for now but is likely to worsen as the wreck continues to deteriorate and expose more explosive material.

The North Sea holds large numbers of such wrecks from both world wars: an estimated 190,000 mines were laid there during World War I, and the Battle of Jutland off northern Jutland sank more than 25 ships and killed nearly 10,000 sailors. In a 2024 report for the Danish Environmental Protection Agency, Andresen identified 10,127 wrecks in Danish waters, around 15% of them dating to the two world wars.

Andresen said Germany is further along than Denmark in retrieving and neutralizing explosives from wrecks in the Baltic Sea, though the process is costly, and that detonating munitions underwater can sometimes disperse contamination rather than contain it. As part of the international REMARCO project, researchers are also testing crawling seabed robots that can map the location of dangerous munitions and, in some cases, retrieve and neutralize them.